1. Field of the Invention
The present invention relates to diaphragm valves. In particular, the present invention relates to diaphragm valves which allow for free-drainage of a valve body of the valve when the valve is in the open position.
2. Description of Background Art
The demand for higher quality products forces industries to continually reevaluate fundamental and basic elements of their processes in a search to discover new methods and better components that will yield greater uniformity with higher levels of reproducibility in order to achieve the quality desired. Evaluation of inspection results by United States Food and Drug Administration (FDA) inspectors in recent years has caused that agency to push industry to focus on cleaning validation and, of particular relevance to this disclosure, the cleanability of equipment, a large part of which is sanitary valving. Among the concerns are that some equipment in these processes may not be adequately cleanable in place, that in-situ cleaning procedures are not themselves adequate to clean the equipment installed or that the procedures and equipment are appropriately matched, but the procedures are not being properly executed.
Valves are by far the largest category of equipment used in processes. Relative to other existing valve designs, weir-style diaphragm valves are simple, provide good process isolation, cost-effective to install and maintain and because they were thought to be easily and reliably cleanable in place. Unlike several other categories of valve designs, weir diaphragm valves generally offer good drainability with little hold-up of material when properly installed. For these reasons they have, over the last fifty years, become the valve of choice for use in hygienic processes.
In recent years the performance of these valves has been subject to much greater and closer scrutiny, at least in part due to pressure from FDA. While still the preferred choice for some applications, it has become apparent that weir diaphragm valves can pose a significant risk as a source of cross over contamination, particularly if improperly installed, operated and maintained or if clean-in-place and sterilize-in-place procedures are not properly followed. These concerns stem from the basic design of weir diaphragm valves. Referring to FIG. 10 of the present invention, a typical weir diaphragm valve 101 is illustrated. The weir diaphragm valve 101 includes a valve body 103, a diaphragm 133 and a bonnet, as well as other typical valve components (all not shown).
In FIG. 10, a static perimeter or circumferential seal 136 is formed between the valve body 103 and the bonnet by a perimeter of the diaphragm 133. Furthermore, a dynamic line seal 137 is formed along a weir 140. The main problem with the weir diaphragm valve design is that the static circumferential seal 136 is continuous with the line seal 137 made by the diaphragm 133 across the top of the weir 140. When the center portion of the diaphragm 133 is raised to break the line seal 137 across the weir 144 to allow for flow through the valve, pressure is applied to the inner edge of the diaphragm 133 where it forms the static circumferential seal 136 with the valve body 103. Accordingly, a portion of the static circumferential seal 136 is also raised. When the line seal 137 is reformed across the weir 140 by lowering the diaphragm 133, material is trapped between the inner edge of the diaphragm 133 and the valve body 103, i.e., within the static circumferential seal 136. This trapped material may migrate back into the internal cavity 113 of the valve body 103 over time. Although this may be less of a problem while a batch of a process is in progress, not completely removing the trapped residual during cleaning procedures between batches is a more serious issue and may be considered very critical between campaigns of different products by the FDA.
In addition to the above, weir valves in the past were typically used in an orientation where the flow through the valve proceeded from the inlet passage to the outlet passage by flowing vertically over the weir 140. Accordingly, material would be trapped on the upstream side of the internal cavity 113. This of course causes cross contamination.
Manufacturers today, in an effort to improve drainage through their valves and minimize hold-up, recommend that weir diaphragm valves be cantilevered over onto the side so that fluids can flow passively around the weir and out, rather than vertically over the weir. While this is necessary in order to make weir valves drain, this also places a portion of the circumferential seal 136 at the bottom of the valve, causing it to become a sump where material will tend to collect and where complete drainage will be very difficult to fully achieve. Consequently, a more significant cleaning challenge and possible point source for cross contamination is exacerbated when using a weir valve in this manner. Several articles can be found through the literature on the subject of weir-style valve cleanability. One of the most recent is an article in Pharmaceutical Processing (September, 2001, pg. 80) in which the author, in a comparison study of weir valves and radial diaphragm valves, demonstrates that weir valves frequently do not become fully cleaned. In this study, radial diaphragm valves provided much higher clean-in-place reliability.
Accordingly, the primary alternative valve design to weir valves that has gained favor in many industries is the radial diaphragm valve, similar to the testing in the study mentioned above. FIG. 11 of the present invention illustrates a typical radial diaphragm valve 101. As with weir diaphragm valves, radial diaphragm valves include a flexing diaphragm 233 that allows the valve 201 to be opened and closed while segregating the mechanical elements of the valve 201 from the process. Radial diaphragm valves, however, differ from weir diaphragm valves in several important ways. The most important advantage radial diaphragm designs offer is that the static circumferential seal 236 between the valve body 203 in a radial diaphragm valve is not continuous with the dynamic seal 237, as is the case with weir valves. Since the two seals are not continuous, a radial diaphragm valve can be actuated without the circumferential seal 236 being affected. Accordingly, cross contamination as a result of residual hold-up in the circumferential seal 236 is effectively eliminated when compared to the weir diaphragm valve.
While it would seem that the solution to the cross contamination problems currently plaguing the industry could be resolved by radial diaphragm valves, it is a byproduct of the radial design that makes radial diaphragm valves a less perfect solution to the problem. As mentioned above, radial diaphragm valves are defined by the segregation of the circumferential seal 236 from the flow control or dynamic seal 237 and the passage it seals. A review of the background art will show that in the dynamic seal 237, the flow control passage 224 and the mating annular dynamic sealing surface 237 immediately about it are positioned at the center of the internal valve cavity. Accordingly, the flexible portion 241 of the diaphragm 233 between the static circumferential seal 236 and the dynamic seal 237 is enough to allow the necessary range of movement of the dynamic sealing tip 235 of the diaphragm 233 to seal the flow control passage 244, while minimizing stress on the flexible portion 241 of the diaphragm 233. In view of this, the portion of the diaphragm 233 which mates with the valve body 203 at the circumferential seal 236 is not lifted. Accordingly, material is not trapped in the circumferential seal as in a weir valve.
As can be readily understood, with the arrangement of radial diaphragm valve, an opening into the internal cavity 213 of one flow passage 226 is located radially outward from the centrally placed flow control passage 224 and radially inward from the circumferential seal 236. It will also be noted that the surface of both of these passages open into the valve internal cavity 213 through the same wall 242. The wall 242 is substantially planar or dished as illustrated in FIG. 11, and at least one of the axes of the flow passages tends to enter the internal cavity 213 at close to a right angle.
As a consequence of the combination of the orientation of the passages relative to the wall 242 of the internal cavity 213 through which they enter, the opening of one fluid passage 224 is positioned centrally in the internal cavity 213 with the other passage 226 positioned radially. Furthermore, both passages are within the circumferential seal 236. Accordingly to the background art, radial diaphragm valves can only be made to fully drain if they are oriented vertically, i.e., with the outlet at the bottom, and will only drain if the bottom of the outlet is adjacent the circumferential seal 236. Accordingly, in FIG. 11, it would be necessary to orient the valve 201 such that the passage 226 is oriented downward.
As can be readily understood, since radial diaphragm valves are only completely drainable if oriented in a vertical manner, there are severe limitation on how radial diaphragm valves found in the background are can effectively be used. Specifically, orienting a radial diaphragm valve in a vertical orientation results in a significant vertical drop across them. Due to the numerous valves required for some systems, orienting all of the valves in a vertical manner is not possible because of the space limitations. Accordingly, radial diaphragm valves have not displaced weir diaphragm valves in practice, in spite of the in-situ cleanability limitations of weir diaphragm valve designs.
Having described the strengths and weaknesses of the two predominant categories of valves used for hygienic processing, the present inventor would like to present a new alternative valve design that combines the best features of each of the design categories discussed above, while eliminating weaknesses. As will be seen in the present invention, it is possible to construct a valve design that can incorporate the desirable diaphragm sealing component wherein the dynamic seal is segregated from the static circumferential seal, where the process contact surfaces of the valve body and of the diaphragm are fully accessible to the process flow without the creation of pooling areas, breathing seals or additional crevice areas so that cleaning and sterilizing the valve in place can most effectively be achieved.
The present invention has the added benefit of being a compact design that may also be manufactured economically due, in part, to the open nature of the internal cavity and passages formed in the valve body. Furthermore, when constructed as an embodiment where inlet and outlet passages are coaxial, the present invention has the benefit of being bilaterally symmetrical, allowing it to be used, without modification and without any loss in operational effectiveness, in right- or left-handed applications, requiring only that the body be rotated. The valve of the present invention also provides improved flow with better self-cleaning and sterilizing characteristics because of the minimization of quiet zones and the sweeping scouring flow path that will be created as material flows into and out of the internal valve cavity.
It is a primary object of the present invention to provide a device that can be effectively cleaned and sterilized in place, where the process can effectively be isolated from the mechanical valve elements through the use of a diaphragm or other effective sealing members and where unobstructed free-drainage through the valve can still be achieved.
A further object of the present invention is to allow flow through the valve without requiring a step up or a step down of flow and to do so without the accumulation of material flow in the valve body as currently happens with background art radial diaphragm valves.
Yet another object of the invention is to provide a dynamic diaphragm seal for reversibly sealing off the flow of process through the valve that is separate and discrete from the static seal that forms between the diaphragm and the valve body such that when the dynamic seal is actuated, the static seal remains essentially unaffected. Accordingly, the static seal does not tend to accumulate and harbor materials along the seam between the diaphragm and the valve body as currently occurs with weir-style diaphragm valves.
Still another purpose of the present invention is to provide a design that can be effectively cleaned and sterilized in place.
Yet another purpose of this design is to provide a design that can be made with an o-ring seal or with a diaphragm seal.
Another object of this invention is to provide a device that can be easily is dismantled, inspected and maintained.
Another object of the present invention is to provide an apparatus that can be operated manually or automatically.
Still another object of the invention is to provide a device that can be modified and combined to form valve with inlets and outlets oriented at different angles from one another such as in the case of an xe2x80x9cLxe2x80x9d shaped valve, form valves with single or multiple inlets and/or outlets such as in the case of a xe2x80x9c2-wayxe2x80x9d valve, form compound valves where a single body can combine several internal cavities, inlets and outlets which may or may not be interconnected.
The above objects of the present invention can be accomplished by providing a valve body with the following construction. A valve body having an internal cavity formed therein. An inlet passage and an outlet passage are formed in the body. The inlet passage has an inlet opening in communication with the internal cavity, and the outlet passage has an outlet opening in communication with the internal cavity. A circumferential sealing surface is formed on a wall of the internal cavity. At least a portion of the circumferential sealing surface extends between the inlet opening and the outlet opening and circumferentially around the internal cavity. Furthermore, a continuous unobstructed path for flow along the valve bottom extends through the inlet passage, the internal cavity and the outlet passage that forms a coplanar surface to allow for free-drainage of the body.
The valve of the present invention may be equipped with a radial diaphragm sealing element or an o-ring seal, may be actuated manually or automatically and may be formed as a single valve or ganged together as a flow control unit encompassing multiple flow pathways and multiple internal cavities.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.